THE SON of a school caretaker has been warned to expect jail, after being convicted of unlawfully making a bomb.

David Riding was found guilty of manufacturing a 13cm-long pipe bomb without a lawful purpose at Durham Crown Court today, following a three-day trial.

Police found the device, which had "killer" scratched onto its side, with a knuckle duster, imitation guns, knives and blank ammunition, in a locked safe hidden under Riding's bed in November last year.

Riding lived in the grounds of Durham High School for Girls, where his father is a caretaker.

During his trial, Riding, who was described in court as a "bedroom Rambo" claimed he made the pipe bomb to see if he could.

But Judge Christopher Prince rejected the reasoning, saying the 20-year-old was "an extremely disturbed young man".

"There have been the most appalling tragedies within schools created by people going in armed with weapons.

"He would have had such a stock of weapons he would have been in the position to go into the school with knives stuck out of his belt and a knuckle duster to protect himself, two guns which looked very realistic, 47 cartridges and an improvised explosive device that may have had a lethal capability, scrawled upon which are words which demonstrate to me some form of resentment to other persons, namely killer and other obscenities."

The case was adjourned to Friday, January 23, for a psychiatric report to be compiled.

Riding, of Lake View, Station Town, east Durham, was remanded in custody.